Compound interest calculator
Money & financeHow much will your savings grow with compound interest?
See your final balance, what you put in and the interest earned, year by year.
Savings
What you enter stays on your device while you use this tool. Opening a shared link sends the settings in its address to HowToolbox to prepare the page.
Regular deposits
Final balance
€68,229.77
After 20 years: €34,000.00 put in, €34,229.77 interest earned.
Nominal amounts before tax, fees and inflation, at a fixed rate. Real returns vary.
What the balance is made of
- Money put in €34,000.00 · 50%
- Interest earned €34,229.77 · 50%
= Final balance €68,229.77
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Savings growth by year
Over 20 years the money put in grows to €34,000.00 and the interest earned to €34,229.77.
- Money put in
- Interest earned
| Year | Deposits | Interest | Money put in | Interest so far | Balance |
|---|---|---|---|---|---|
| 1 | €1,200.00 | €539.50 | €11,200.00 | €539.50 | €11,739.50 |
| 2 | €1,200.00 | €628.50 | €12,400.00 | €1,168.01 | €13,568.01 |
| 3 | €1,200.00 | €722.05 | €13,600.00 | €1,890.06 | €15,490.06 |
| 4 | €1,200.00 | €820.39 | €14,800.00 | €2,710.44 | €17,510.44 |
| 5 | €1,200.00 | €923.75 | €16,000.00 | €3,634.20 | €19,634.20 |
| 6 | €1,200.00 | €1,032.41 | €17,200.00 | €4,666.60 | €21,866.60 |
| 7 | €1,200.00 | €1,146.62 | €18,400.00 | €5,813.23 | €24,213.23 |
| 8 | €1,200.00 | €1,266.68 | €19,600.00 | €7,079.91 | €26,679.91 |
| 9 | €1,200.00 | €1,392.88 | €20,800.00 | €8,472.79 | €29,272.79 |
| 10 | €1,200.00 | €1,525.54 | €22,000.00 | €9,998.32 | €31,998.32 |
| 11 | €1,200.00 | €1,664.98 | €23,200.00 | €11,663.30 | €34,863.30 |
| 12 | €1,200.00 | €1,811.56 | €24,400.00 | €13,474.86 | €37,874.86 |
| 13 | €1,200.00 | €1,965.64 | €25,600.00 | €15,440.50 | €41,040.50 |
| 14 | €1,200.00 | €2,127.60 | €26,800.00 | €17,568.09 | €44,368.09 |
| 15 | €1,200.00 | €2,297.84 | €28,000.00 | €19,865.93 | €47,865.93 |
| 16 | €1,200.00 | €2,476.80 | €29,200.00 | €22,342.73 | €51,542.73 |
| 17 | €1,200.00 | €2,664.91 | €30,400.00 | €25,007.64 | €55,407.64 |
| 18 | €1,200.00 | €2,862.65 | €31,600.00 | €27,870.29 | €59,470.29 |
| 19 | €1,200.00 | €3,070.50 | €32,800.00 | €30,940.78 | €63,740.78 |
| 20 | €1,200.00 | €3,288.99 | €34,000.00 | €34,229.77 | €68,229.77 |
See your final balance, what you put in and the interest earned, year by year.
How to use
- Enter the amount you start with and the deposit you add regularly (0 if you add nothing).
- Choose whether you deposit every month or every year, and whether the deposit goes in at the start or the end of the period.
- Enter the yearly interest rate, how often interest is added and how many years you save.
- Read the final balance, then open the table for each year, copy it or download it as a CSV file.
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How it works
Compound interest means interest earns interest. Each time interest is added to the account, the next interest is calculated on the larger balance, so growth speeds up over time. Regular deposits add to the balance and start earning interest too.
A starting amount P grows to A = P(1 + r/n)^(nt), where r is the yearly rate as a decimal, n the number of times interest is added per year and t the number of years.
Regular deposits grow the same way, each from the day it goes in. A deposit made at the start of a period earns one period more interest than one made at the end. For example, 100 a month for a year at 1% a month adds up to 1,268.25. These are the standard compound interest and annuity formulas.
The result assumes the rate stays the same for the whole period. It ignores taxes, account fees and inflation, so it is a nominal estimate, not a promise of returns.
Worked example
How much does €1,000.00 grow at 5% a year for 2 years without deposits?
- €1,000.00 × (1 + 5 ÷ 100)^2 = €1,102.50.
€1,102.50, including €102.50 interest, compounded annually.
Frequently asked questions
Does it matter whether I deposit at the start or the end of the month?
A little: a deposit made at the start earns interest for one extra period, so the part of the balance built from deposits ends up one period's interest larger.
Why does compounding more often give slightly more?
Interest added more often starts earning interest sooner. At the same yearly rate, monthly compounding gives a little more than yearly, and daily a little more than monthly, but the gap is small.
Is this what my investments will be worth?
Only if they grow at exactly this rate every year. Shares and funds go up and down, and taxes, fees and inflation reduce what you keep.
How much does 200 a month grow to?
At 7% a year, compounded monthly, 200 a month grows to about 104,000 in 20 years, of which 48,000 is what you paid in. After 25 years it is about 162,000. Funds do not return a fixed rate, so try a lower one too.
Can I calculate growth without adding deposits?
Yes. Set the regular deposit to zero; only the starting amount earns interest.
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